My A10 is a 1959 bitsa but hopefully the same.
Outer cable is 12.5 inches
Inner cable is 20.25 inches measured between the centre of the nipples. Front nipple is a ball; rear is a barrel.
There is an adjuster at the rear bracket that is open by about 0.5 inches but this does not effect the lengths given above.
Venhill.co.uk will sell you all the bits or will make up a cable to your specification - not sure what the price for a made up cable is but they seem quite reasonable